Solvatochromic solvent polarity measurements and selectivity in reversed-phase liquid chromatography

The ET(30) polarity values of binary acetonitrile-water and methanol-water mobile phases, used in reversed-phase liquid chromatography, were measured and compared with methylene selectivity (alpha CH2) for both traditional siliceous bonded phases and for a polystyrene-divinylbenzene resin reversed-phase material. The variation in methylene selectivity for both was found to correlate best with percent organic solvent in methanol-water mixtures, while the ET(30) polarity provided the best correlation in acetonitrile-water mixtures. The polymeric resin column was found to provide higher methylene selectivity than the siliceous bonded phase at all concentrations of organic solvent.